1. Field of the Invention
The present invention relates to a marker for identifying an object in a system which includes a source of irradiance and a detector of light reflected from the marker. More particularly, the present invention relates to a removable data storage cartridge and to a data storage drive for receiving the cartridge. Even more particularly, the present invention relates to detecting the presence of the correct disk cartridge in the data storage drive by use of a retroreflective marker on the cartridge.
2. Description of the Prior Art and the Problems Solved by the Invention
Disk drives for receiving removable disk cartridges, including conventional 3.5" floppy disk drives, must have some mechanism for detecting the insertion or presence of a disk cartridge in the drive. The actuator that carries the recording heads of the disk drive across the recording surfaces of the disk should not be allowed to move unless the presence of a disk cartridge is detected. In the prior art, mechanical switches are typically employed to detect the presence of a disk cartridge within the drive. Such switches are typically positioned such that when a disk cartridge is inserted fully into the drive, the cartridge contacts the switch, thereby providing an indication that the disk cartridge is present.
The above identified parent application entitled "Retroreflective Marker for Data Storage Cartridge" describes the reflection of a highly concentrated quasi circular lobe of light whose spread on reflection is captured by the aperture of a phototransistor in close proximity to a light emitting diode (LED). This emitter/detector pair is in the drive and a retroreflective array is on the cartridge. The desired light lobe size is provided by the geometric size of the retroreflector array elements relative to the spacing of the emitter and the detector in the drive. Due to this physical size matching and the fact that retroreflectors are used, this marker on the cartridge is quite insensitive to cartridge tilt and distance from the emitter/detector pair in the drive.
Recently, very small mini-cartridges have been developed for use in miniature disc drives. These mini-drives are incorporated into hand-held devices such as digital cameras, electronic books, global positioning systems, cellular phones and the like. "INTERCHANGEABLE CARTRIDGE DATA STORAGE SYSTEM FOR DEVICE PERFORMING DIVERSE FUNCTIONS", U.S. Ser. No. 08/746,085 filed Nov. 11, 1996, Edwards, et al. now U.S. Pat. No. 5,809,320 (Attorney's Docket IOM-9319) describes such mini-cartridges, mini-drives, and hand-held devices. This application is incorporated herein by reference.
The mini-cartridge's data storage disk has a total thickness of about 2.5 mm. As disk storage products become smaller and smaller the need for a cartridge marker of thinner physical size is required. The aforementioned mini-cartridge has such a requirement. The present invention provides a solution to this requirement while maintaining the functionality of the retroreflector invention.
The ability to discriminate between cartridge types after insertion into a data storage device but prior to putting the read/write heads on the recording media is of significant value and utility. Principally this utility comes from the ability to detect the difference between various capacities or generations of data storage cartridges in a downward media compatible data storage drive. This discrimination capability allows for drive/media specific adjustments to be made such as media rotation rate, data channel rates, location of Z track for initial seeking, or even mechanical adjustment in the drive like the active engagement of new crash stop locations.
A "caddy" cartridge, as mentioned in the aforementioned Edwards, et al. application provides cross drive platform compatibility, for example between mini-cartridges and personal computer cartridges. The ability to recognize the installation of a "caddy" into the drive prior to spinning up of the "caddy" and loading of heads is necessary. Again rotational speed adjustments, Z track location information, data channel rate and crash stop/ID and OD data track location information must be determined prior to read/write head loading. This invention provides a solution of these problems also.
Another problem associated with the detection of LED light reflected from any reflective material is the occurrence of illuminance hot spots or structure in the LED output which often results in uneven illumination of the cartridge marker. Since these are typically randomly located the effect on the amplitude of the reflected return is variable. A smoothing or homogenizing of reflected light in this type of system would be a significant improvement in system to system reliability.